1. Field of the Invention
The present general inventive concept relates to an image forming apparatus, and more particularly to an image forming apparatus in which paper is fed while being attached to a paper feed body.
2. Description of the Related Art
An image forming apparatus is an apparatus that prints an image on a printing medium, e.g., paper, according to an inputted image signal. One example of the image forming apparatus is an electrophotographic image forming apparatus. The electrophotographic image forming apparatus is configured such that a light beam is scanned across a photosensitive body charged with a predetermined electric potential to form an electrostatic latent image on the outer peripheral surface of the photosensitive body. The electrostatic latent image is developed into a visible image by supplying a toner to the electrostatic latent image, and the visible image is transferred and fixed onto paper. An electrophotographic color image forming apparatus is configured such that toners of different colors are supplied to respective photosensitive bodies to form images of different colors, and the images of different colors are overlapped and transferred onto paper to achieve a color image.
FIG. 1 is a view illustrating a conventional color image forming apparatus. As illustrated in FIG. 1, the conventional image forming apparatus includes four developing devices 1Y, 1M, 1C, and 1K, in which toners of different colors, e.g., yellow (Y), magenta (M), cyan (C), and black (K), are respectively contained, a paper feed belt 3 which rotates while contacting photosensitive bodies 2Y, 2M, 2C and 2K provided respectively in the developing devices 1Y, 1M, 1C, and 1K, and a paper attaching roller 4 which attaches a printing medium, e.g., paper P to the paper feed belt 3.
When the paper is fed between the paper attaching roller 4 and the paper feed belt 3, a high voltage is applied to the paper attaching roller 4. Accordingly, the paper is attached to the paper feed belt 3 by an electrostatic force, and is fed at the same velocity as a traveling velocity of the paper feed belt 3.
The developing devices 1Y, 1M, 1C, and 1K develop electrostatic latent images formed on the respective photosensitive bodies 2Y, 2M, 2C, and 2K into yellow, magenta, cyan, and black toner images according to color image information transmitted to the image forming apparatus. The yellow, magenta, cyan and black toner images are then overlapped and transferred onto the paper in sequence, thereby achieving a color toner image on the paper.
The external housings of the developing devices 1Y, 1M, 1C, and 1K are designed such that spaces SY, SM, SC, and SK are formed between each of the housings of the developing devices 1Y, 1M, 1C, and 1K and the paper feed belt 3 to install the paper attaching roller 4 therein. However, the paper attaching roller 4 is only installed in one of the spaces SY, SM, SC, and SK formed among the developing devices, and thus the remaining unused spaces are superfluous. For instance, the space SY, which is formed between the paper feed belt 3 and the developing device 1Y and disposed on the uppermost paper stream side in a feeding direction of the paper, is a useful space in which the paper attaching roller 4 is installed. But, the spaces SM, SC, and SK, which are formed between the paper feed belt 3 and the other developing devices 1M, 1C and 1K, create an unnecessary waste of space.
In order to solve the above problem, two solutions have been implemented to alter the design of the external housings of the developing devices. With the first solution, the external housings of the developing devices were designed so that only the developing device 1Y on the uppermost stream side includes the space for installing the paper attaching roller 4. Alternatively, with the second solution, the external housings of the developing devices 1Y, 1M, 1C, and 1K were designed without the spaces being formed between each of the respective developing devices 1Y, 1M, 1C, and 1K and the paper feed belt 3. Thus, the paper attaching roller 4 is installed below the developing device 1Y. However, the first solution has a shortcoming of the components being incompatible due to the different shape of the developing device 1Y as compared to the other developing devices 1M, 1C, and 1K. The second solution has a shortcoming of an increase in size of the image forming apparatus due to an increase in the height of the set of developing devices by the size of the paper attaching roller 4.
As illustrated in FIG. 1, the paper attaching roller 4 of the conventional image forming apparatus is pressed toward the paper feed belt 3 by the elastic force of a spring (not shown). If the force exerted to press the paper attaching roller 4 is greater than a predetermined reference value, when the front end of the paper P advances to the paper attaching roller 4 or the rear end of the paper leaves from the paper attaching roller 4, the feeding speed of the paper P cannot be maintained at a constant speed as it is guided along the paper feed belt 3 due to the excessive pressing force. The inconsistent feeding speed of the paper causes deterioration of image quality, e.g., color discordance. On the other hand, if the force of pressing the paper attaching roller 4 is less than the predetermined reference value, the paper attaching roller 4 may easily separate or dislodge from the image forming apparatus as a result of any external jolts or shock to the image forming apparatus.
Further, as the image forming apparatus is used over a long period of time, paper dust or residual toner particles accumulate inside of the image forming apparatus during the developing process. Thus, another drawback of the conventional image forming apparatus is that the outer peripheral surface of the paper attaching roller 4 is easily contaminated with dust from the paper P dust or toner particles.